When painting window frame and trim materials there is always the attendant problem of keeping the paint off the glass, while at the same time in order to protect the frame or trim from moisture, sealing the juncture between the trim and the glass with paint. Normally, the paint is applied in a narrow band on the glass surface adjacent the trim, but this method can be difficult and time-consuming, requiring an inordinate painting skill. Another less exacting method involves painting along the trim-glass junction, sometimes onto the glass, sometimes shy of the glass. While this method may be faster than the previous method, it leaves the trim-glass juncture in an unsealed state. In such cases rain water or indoor condensation will seep into the unprotected interface and eventually cause destruction of the trim materials by rotting or cracking. Also the old paint at the interface will be dried and cracked, thus allowing moisture to seep in at the interface and eventually lift the putty away from the glass to enhance further water penetration.
Still other methods include painting at will on the glass surface or window pane while painting the trim. A scraper or razor blade must then be used to remove the paint. Ordinary latex paint can be scraped off within hours after being applied, but after that short period it will adhere to the glass strongly. When dry, ordinary paint is not a particularly "cohesive" coating and, as such, will then break up, or fracture, when subjected to the sheer forces of the scraper. When paint dries too thoroughly, it must be removed in small pieces, a time-consuming task which often damages the glass.
Yet another method involves masking. With masking, an adhesive coating or tape is placed on the window pane, prior to installation or after installation, so that the trim or frame material can be painted quickly and without regard to the juncture between glass and trim since any excess paint will be applied to the protective coating. This method, however, again requires the time-consuming operation of carefully applying the adhesive coating so that it lines up with and abuts the glass-trim juncture.
To summarize the drawbacks of the above-mentioned methods for protecting window pane glass during a trim or frame painting operation, it will be seen that a high labor commitment is required, involving increased expense, or in the absence of skilled labor, sloppy work in the form of uneven edges of paint residue along the trim-glass interface or juncture, especially after spray painting (and including concrete splatter on the window glass during new construction), or in the case of applying a protective coating for the glass, the time consuming step of applying masking tape or other protective adhesive coating to square up exactly with the glass-trim interface, in which case paint can be drawn under the edge of the tape or coating at the interface by capillary action.